[clang] Fix standalone execution in TableGen/target-builtins-prototype-parser.td (#84186)

Use a path that works for both standalone as well as full repository
builds.

Fixes: 9b672de ("[clang][Builtins] Parse clang extended vectors types. (#83584)")

Author: tuliom

clang/test/TableGen/target-builtins-prototype-parser.td

@@ -1,11 +1,11 @@
-// RUN: clang-tblgen -I %p/../../../clang/include/ %s --gen-clang-builtins | FileCheck %s
-// RUN: not clang-tblgen -I %p/../../../clang/include/ %s --gen-clang-builtins -DERROR_EXPECTED_LANES 2>&1 | FileCheck %s --check-prefix=ERROR_EXPECTED_LANES
-// RUN: not clang-tblgen -I %p/../../../clang/include/ %s --gen-clang-builtins -DERROR_EXPECTED_COMMA 2>&1 | FileCheck %s --check-prefix=ERROR_EXPECTED_COMMA
-// RUN: not clang-tblgen -I %p/../../../clang/include/ %s --gen-clang-builtins -DERROR_EXPECTED_TYPE 2>&1 | FileCheck %s --check-prefix=ERROR_EXPECTED_TYPE
-// RUN: not clang-tblgen -I %p/../../../clang/include/ %s --gen-clang-builtins -DERROR_EXPECTED_A 2>&1 | FileCheck %s --check-prefix=ERROR_EXPECTED_A
-// RUN: not clang-tblgen -I %p/../../../clang/include/ %s --gen-clang-builtins -DERROR_EXPECTED_B 2>&1 | FileCheck %s --check-prefix=ERROR_EXPECTED_B
-// RUN: not clang-tblgen -I %p/../../../clang/include/ %s --gen-clang-builtins -DERROR_EXPECTED_C 2>&1 | FileCheck %s --check-prefix=ERROR_EXPECTED_C
-// RUN: not clang-tblgen -I %p/../../../clang/include/ %s --gen-clang-builtins -DERROR_EXPECTED_D 2>&1 | FileCheck %s --check-prefix=ERROR_EXPECTED_D
+// RUN: clang-tblgen -I %p/../../include/ %s --gen-clang-builtins | FileCheck %s
+// RUN: not clang-tblgen -I %p/../../include/ %s --gen-clang-builtins -DERROR_EXPECTED_LANES 2>&1 | FileCheck %s --check-prefix=ERROR_EXPECTED_LANES
+// RUN: not clang-tblgen -I %p/../../include/ %s --gen-clang-builtins -DERROR_EXPECTED_COMMA 2>&1 | FileCheck %s --check-prefix=ERROR_EXPECTED_COMMA
+// RUN: not clang-tblgen -I %p/../../include/ %s --gen-clang-builtins -DERROR_EXPECTED_TYPE 2>&1 | FileCheck %s --check-prefix=ERROR_EXPECTED_TYPE
+// RUN: not clang-tblgen -I %p/../../include/ %s --gen-clang-builtins -DERROR_EXPECTED_A 2>&1 | FileCheck %s --check-prefix=ERROR_EXPECTED_A
+// RUN: not clang-tblgen -I %p/../../include/ %s --gen-clang-builtins -DERROR_EXPECTED_B 2>&1 | FileCheck %s --check-prefix=ERROR_EXPECTED_B
+// RUN: not clang-tblgen -I %p/../../include/ %s --gen-clang-builtins -DERROR_EXPECTED_C 2>&1 | FileCheck %s --check-prefix=ERROR_EXPECTED_C
+// RUN: not clang-tblgen -I %p/../../include/ %s --gen-clang-builtins -DERROR_EXPECTED_D 2>&1 | FileCheck %s --check-prefix=ERROR_EXPECTED_D
 
 include "clang/Basic/BuiltinsBase.td"